Abstract: A hole boring charge assembly suitable for explosively forming a wide borehole in a concrete target consists of a detonatable array of at least three hollow charges (12) having recessed, lined forward faces (14) facing towards the target in the same general direction as a fore-and-aft line of target penetration. Simultaneous detonation of the charges (12) produce individual jet penetrators derived from the charge liners (16) which penetrate the target and together produce a wide multi-sided borehole therein suitable for the subsequent emplacement of a blasting charge. The charges (12) may be focussed forward of the array to produce a single, coalesced penetrator which is capable of producing a wide, tapered, approximately axisymmetric hole in concrete.